The muffler heat shield may become loose on the muffler causing a rattle or popping noise. Our technicians tell us there is a kit available from GM to correct this problem.Google+
Car Problem Reports
GMC Yukon Denali Popping Noise From Muffler Heat Shield
GMC Yukon Denali Problem
Visitor, 2004 GMC Yukon Denali, 113,400 mi
the heat shield became loose and was very noisy. Ended up removing the shield. It isn't really necessary just more garbage that they put on so you can go get an expensive repair from the dealer.